This invention is directed to a storage rack for the high density storage of spent nuclear fuel assemblies.
Each nuclear electric generating station must safely store its spent fuel assemblies. At one time, it was expected that these fuel assemblies would be stored at the site of the generating station only a short time before the assemblies were shipped to a central plant for reprocessing. However, there are no reprocessing plants in operation to date, therefore, the spent fuel assemblies have to be stored at the power plant site. It has been thought that such shipment would endanger the public in case of accident. For the storage of spent nuclear fuel assemblies, each nuclear powered electric generation station has on its site a spent fuel pool. This is a water-filled pool into which the spent fuel assemblies are placed for storage. The water serves as a coolant and also serves as a radiation shield so that the radiation level around the pool is sufficiently low as to be safe for workers in that area. A particular advantage of water is that it is transparent so that the pool can be inspected while the radiation shielding and cooling functions are fully effective.
With the requirement for more spent fuel assembly storage capacity, higher density storage is required. Some attempts at fuel assembly and storage rack design have resulted in vertical placement of the spent fuel assemblies in a rack structure which utilizes a continuous integral support base on which the fuel assemblies rest. These designs transfer the vertical loads to the pool floor at just a few locations, and since the vertical loads are significant, the rack structure has to be substantial to carry the load to the floor.